Microwave scanning system



June 21, 1955 R. H. RINES MICROWAVE SCANNING SYSTEM Original Filed Oct.9, 1944 P0455 k/raaqme Mew/live Patented June 21,

Free

2,711,441) MICROWAVE SCANNING SYSTEM Robert Harvey Rines, Brookline,Mass.

Original application October 9, 1944, Serial No. 557,807,

new Patent No. 2,553,606 dated May 2 2, 1951. Dizilded rand thisapplication August 23, 1345, Serial No.

34 Claims. (Cl. 178-63) The present invention relates to microwavescanning systems, and more particularly to radioreceiving systems that,while having more general fields of usefulness, are especially adaptedfor use in television. The present application is filed inpursuance to arequirement for division of application Serial No. 557,807, filedOctober 9, 1944 now Patent No. 2,553,606 issued May 22, 1951.

An object of the invention is to provide a new and improvedradio-receiving system.

further object is to provide a new and improved antenna system.

An additional object is to provide a novel system embodying a cavityresonator.

A further object is to provide a new and improved wave-guide structure.1

Still an additional object is to provide a novel scanning antennasystem.

Another object is to and-television system.

Another object of the present invention is to provide a new and improvedradio-locator system for both detecting the presence of a body andrendering it visible.

Other and further objects will be explained hereinafter and will be moreparticularly pointed out in the appended claims. 7 l v The inventionwill now be more fully expalined in con nection with the accompanyingdrawings, the single figure of which is a diagram showing an airplaneobject from which radio waves are reflected and scattered to' areceiving system in accordance with the present invention.

provide a novel combined radio- An electromagnetic wave generator 4 isshown exciting A a dipole 2 to produce ultrahigh-frequency microwavepulsed-radio energy, say, of 3 or 1.5 centimeters wavelength. Acontinuous-wave or any other type of modulated-wave generator may beemployed,'but pulsed energy, at present, has the advantage of economicaland easy high-power ultra-high-frequency generation.

The waves emitted by the dipole 2 may be directed by a reflector 3 upona parabolic reflector 6. The parabolic reflector 6 is shown directingthe waves in any desired direction, for example, toward an object, say,an airplane 8, from which they are reflected and scattered toward areceiving station.

At the receiving station, the radio waves thus reflected and scatteredfrom the object 8 may be focused by an electromagnetic dielectric lens5, such as polystyrene, upon a closed-ended resonant-cavity wave-guidecylinder 7. The dielectric lens may be replaced by any other type ofwell-known lens, mirror or other directive system for focusing theelectromagnetic energy scattered or reflected from the object 8 on thecavity cylinder 7.

The resonant-cavity cylinder 7 is provided with a longitudinallyextending slot opening 10. In the preferred construction illustrated,the slot 10 is disposed substantially parallel to the axis of thecylinder and lies substantially in part only of the focal region of thefocusing device 5. In the position shown, the slot 10 is in theright-hand side wall of the cylinder 7 facing the focusing device 5 inorder, as hereinafter explained, to provide a novel technique forexcitation of the wave-guide chamber 7. The cylinder 7 is provided witha member 47 fixed rigidly to one of the closed ends of the cylinder,which member 47 is disposed to rotate axially and rigidly with thecylinder on bearings 45 within a concentrically coaxially arrangedadjacent outer-sleeve cylinder 12. The outer cylinder 12 may besupported upon semi-circular roller bearings, not shown in order tosimplify the drawings. The cylinder 12 is provided with a plurality ofsets of apertures or slots 14, 16, 18, 29 and 22, the slots of each setbeing helically disposed along the cylinder 12. The rotation of thecylinder 7 is effected in the direction of the arrow A by means of asynchronous motor 24, driving a shaft fixed to the other end of thecylinder 7. A motor 26 similarly rotates the cylinder 12 in the samedirection, indicated by the arrow B; but not in synchronism with therotation of the cylinder 7.

Assuming, for the moment, the cylinder 7 to be stationary, and thecylinder 12 to be rotating, the radio waves reflected from the airplane8 will enter the resonant chamher 7 at successively spaced positionsalong the preferably substantially parallel slot 10, through the slots14, 16, 18, 20 and 22.

As a result of this construction, therefore, during the rotation of thecylinder 12 through an angle such that the slots 14, '16, 18, 20 and 22become successively aligned with the slot 10, radio waves reflected orscattered from the object 8 will be focused by the lens 5 at successivepositions along the slot 10 from right to left. In effect, therefore, ahorizontal element of the airplane object 8 will become scanned alongthe slot antenna 10 during this part rotation of the cylinder 12.

Preferably, the cylinder 7 may fit' more or less snugly within thecylinder 12, to prevent energy losses through the opening 10. To thesame end, the slot 10 may be made quite narrow, consistent with thedimensions and frequencies employed.

The slots 14, 16, 18, 2t) and 22, of course, will all directly receivethe reflected or scattered radio waves through the lens 5simultaneously. Only that one of these "slots at a time, however, thatis aligned with the slot 10 will permit focused radio waves to enter theresonant chamber 7 through the slot 10, the remaining unaligned portionsor parts of the slot 10 being blocked or closed and thus effectivelyshort-circuited by the sleeve 12. The respective slot antennas 14, 16,18, 20 and 22 will each thus render successive portions of the slot 10effective to permit the entry into the resonant chamber 7 through theslot 10 of a radio-frequency voltage corresponding to the scatteringfrom corresponding regions of the object 8. The wave-guiding slots 14,16, '18, 2d and 22 will thus receive diiferent field strengths of radioenergy, corresponding to the amount of energy reflected or scatteredfrom the various parts of the elemental regions of the object 8 andconverged upon them by the lens 5.

The energy thus received in the resonant chamber 7 excites the same andis picked up by a probe or coupling loop or other antenna 30, whichconstitutes an extension into the chamber 7, through one end thereof, ofthe inner conductor' 34 of a coaxial line, the outer conductor of whichis shown at 32. The coaxial line 32, 34 is shown as a 'rigid linepassing through the member 47, and such that the rotation of the member47 and of the cylinder 7 does not result in rotation of the coaxial line32, 34. This result may be effected with the aid of a bearing 43, whichmay also prevent leakage of energy out of the cavity; for example, itcould be dimensioned in any well-known manner to provide a quarter-wavetrap. The coaxial-line is shown feeding an amplifier ;46, and theamplifier 46 is shown feeding a rectifier 48. The radio energy receivedin the cavity resonator becomes thus transduced into electrical signals,thereby producing an electrical indication of the reception of the radiowaves. The rectifier 48 is connected by a conductor 85 to the controlelectrode 92, and by a conductor 87 to the cathode 94, of the tube part88 of a display oscilloscope 90. It will be understood that all theouter conductors of the coaxial cables have a common connection toground (not shown).

Electrons emitted from the cathode 94 will become enabled, in responseto the action of the electrical signals in the amplifier 46 and therectifier 48, to pass by the control grid 92 toward the anode 96 of thetube part 88 of the oscilloscope 90. The electrons will continue totravel in a stream from the anode 96, between a pair of verticallydisposed deflector plates 98 and 190, and between a pair of horizontallydisposed deflector plates 1G2 and 104, to impinge finally on thefluorescent viewing screen 1% of the oscilloscope 90. Ahorizontal-sweeptime base applied to the horizontally disposed deflectorplates 98 and 100 will cause the electron stream from the cathode 94 tobecome deflected horizontally. The horizontal sweep will becomebrightened by the energy fed from the amplifier 46 and the rectifier 48to the control grid 92 of the oscilloscope. Successive energizingvoltages are thus produced from the amplifier 46 and the rectifier 48 onthe control electrode 92 of the tube part 88 of the cathode-ray-tube 90,of magnitude proportional to the radio-frequency energy received by thecorresponding aligned slots. This will permit the passage of theelectrons, in quantities dependent upon the radio-frequency energy inthe corresponding aligned slots to the anode 96, and between the pairsof deflecting plates 98, 100 and 102, 104, to the viewing screen 106. Avisible picture 123 will thus be produced upon the fluorescent viewingoscilloscope screen 196 of the horizontal scanned line of the airplane.

The above description has proceeded upon the assumpmoreover, the lengthof each of these slots may, as is well known, be related to the full orhalf-wavelength or multiples thereof, such as one-half thehalf-wavelength or one-quarter of the full wave-length corresponding tothe frequency employed. Another pick-up element or probe like the probe38 may then similarly be employed at the other end of the cylinder 7, sothat if there are the proper number of slots in each set, the probeswill receive the radiation, allowed in the resonant chamber 7, in phase,and the two signals may be added into the amplifier 46. It is, ofcourse, to be understood that all dimensions are consistent withstandard wave-guide criteria where the transverse cross-section of thewave guide is sufficient to permit the passage therethrough of radiowaves above a critical frequency related thereto, and that the broadunderlying concept of the present invention is not, of course, dependentupon the particular illustrated shape or configuration of thewave-guiding structures or slots.

This additional pick-up element 50 may be rigidly connected by means ofa stationary coaxial cable comprising an outer conductor 52 and an innerconductor 54, within the cylinder 7, to join with the coaxial line 32,34 so that the additive energy is fed to the amplifier Further probes(not shown) may be inserted in the cylinder at appropriate phasepositions.

A pulse generator 65 may be employed to trigger the horizontaltime-base-sweep circuit 63 and a further pulse generator 64 may beemployed to trigger the verticaltion that the cylinder 7 is stationaryduring the rotation of cylinder 12 and such operation is useful foronedimensional scanning. As the cylinder 7 also rotates in the directionof the arrow A, however, though at a much slower speed, the slot 10 willassume successively lowered positions, thus effecting a periodicscanning of successively lower horizontal elements of the airplane 8.The narrow received radio-wave directivity pattern, therefore, isscanned through an angle subtending the vertical dimension of a scenewhen the cylinder 7 is rotated and is scanned through an anglesubtending the horizontal dimension of the scene when the cylinder 12,interposed between the cylinder 7 and the scene, is rotated.

The vertical-sweep-time base applied to the horizontally disposeddeflector plates 192 and 104 will cause the electron stream to becomedeflected vertically as the slot Eli? becomes gradually lowered.Successively lowered horizontal sweeps, graded in intensitycorresponding to horizontal elements of the airplane 8, will thus beproduced on the oscilloscope screen. The radio-energy picture of theairplane 8, focused by the lens 5 upon the cylinders 7 and 12,therefore, will thus become converted into a visible picture or likeness123 of the airplane upon the screen 106.

Though only five slots lid, 16, 18, 20 and 22 are shown in each set ofslots on the cylinder 12, and though only two sets of these slots areillustrated, it will be understood that this is in order to simplify thedrawing, and that, in practice, there will be many sets of these slots;say, as many as fifty sets, more or less; and that there will be manymore than five slots in each set; say, as many as two hundred more orless; all depending upon the dimensions of the cylinders and thefrequencies of the radio waves employed. In order properly to excite thecavity 7, the frequency of the radio waves should preferably correspondto the resonant frequency of the cavity and, as before stated, the slot1%) may be related to that frequency or wavelength, or multiplesthereof. Preferably,

sweep circuit 69, according to conventional and wellknown televisiontechnique.

For example, the pulse generators may be peak oscillators or, morespecifically, free-running unbalanced multivibrators. The frequency ofthe generator should be adjusted to correspond to the period in which aset of slots 14, 16, 18, 2t} and 22 completely scans the longitudinalslot it A horizontal-time-base sweep will thereby be produced betweenthe vertically disposed deflector plates 98 and 160, corresponding toeach horizontal scan of the slot 10 by the sets of slots 14, 16, 18, 20and 22.

The period of the vertical sweep between the horizontally disposeddeflector plates 102 and 194 should correspond to the period in whichthe slot 15) itself scans, in a vertical sense, the radio-energy picturefocused upon it by the lens 5. This may be accomplished by adjusting thefrequency of the pulse generator 64 to correspond to the period in whichthe slot 10 scans the field converged by the lens 5.

The visible picture 123 of the airplane object 8 on the fluorescentscreen 106 will accordingly correspond to the radio-frequency picture onthe cylinders 7 and 12 which, in turn, corresponds to the actual object8.

Modifications will occur to persons skilled in the art, and all such areconsidered to fall within the spirit and scope of the invention, asdefined in the appended claims.

What is claimed is:

1. An electric system having, in combination, a microwave wave-guidedimensioned to support a predetermined frequency of microwave radioenergy and provided with an opening, means provided with a plurality ofslots disposed substantially parallel to the opening, and means forperiodically alining the opening with successive slots.

2. An electric system having, in combination, a microwave wave-guidedimensioned to support a predetermined frequency of microwave radioenergy and provided with an opening of dimensions resonant to the saidfrequency, and means for periodically blocking parts of the opening.

3. An electric system having, in combination, a micro Wave wave-guidedimensioned to support a predetermined frequency of microwave radioenergy and provided with an opening, means for focusing radio wavescorresponding to the said frequency on the wave-guide, and meansprovided with a plurality of slot antennas for scanning the opening,thereby correspondingly to excite the waveguide.

4. An electric system having, in combination, a microwave radio-wavegenerator, means for transmitting the generated waves through space,microwave wave-guide means dimensioned to support the frequency of thetransmitting means and provided with an opening for receiving thetransmitted waves, and means for rendering various portions of theopening successively effective to receive the radio waves.

5. An electric system having, in combination, a microwave wave-guidedimensioned to support a predetermined frequency of microwave radioenergy and provided with an opening of dimensions sufficient to passwaves of the said frequency, and means comprising a conductive sleevepositioned to cover at least a predetermined part of the said openingfor blocking the said part of the said opening, the sleeve being movablewith respect to the Waveguide to permit the blocking of differentpredetermined parts of the said opening.

6. An electric system having, in combination, a cavity resonatorprovided with an opening in a side wall thereof, means disposed facingthe opening for focusing radio waves received from space upon a focalregion, the opening being dimensioned and positioned substantially inpart only of the focal region in order to cause the focused Waves withinthe said part only of the focal region to impinge upon the opening,thereby correspondingly to excite the cavity resonator, and meansconnected with the excited cavity resonator controlled in accordancewith the focused radio waves for producing an electrical indication ofthe reception of the radio waves.

7. An electric system having, in combination, a cavity resonatorprovided with a slot opening in a side wall thereof, means disposedfacing the opening for focusing radio waves received from space upon afocal region, the slot opening being dimensioned and positionedsubstantially in part only of the focal region in order to cause thefocused Waves within the said part only of the focal region to impingeupon the opening, thereby correspondingly to excite the cavityresonator, and rigid transmission line means connected with andterminating in the cavity resonator for receiving and carrying away theradio-wave energy within the excited cavity resonator to produce anelectrical indication of the reception of the radio waves.

8. An electric system having, in combination, a cavity resonatorprovided with an opening, means disposed adjacent to the resonator forcausing radio waves emanating from an object to scan the opening,thereby correspondingly to excite the cavity resonator, and meansconnected with the excited cavity resonator and controlled in accordancewith the scanning for producing a likeness of the object.

9. A radio-wave system having, in combination, a

cylindrical cavity resonator dimensioned to support a resonant frequencycorresponding to the frequency of the radio waves and provided with alongitudinally disposed opening, and a cylinder in which the cavityresonator is disposed, the cylinder being provided with helicallydisposed means of dimensions resonant to the said frequency of the radiowaves for scanning the opening, thereby to excite the cavity resonator.

10. An electric system having, in combination, a cavity resonatorprovided with an opening, means having a plurality of slots adapted tobe successively alined with the opening, means for relatively moving thecavity resonator and the first-named means to cause radio waves from anobject to scan the opening, thereby correspondingly to excite the cavityresonator, and means connected with the excited cavity resonator andcontrolled in accordance with the scanning for producing a likeness ofthe object.

11. An electric system having, in combination, a cylindrical cavityresonator provided with a longitudinally disposed opening, a cylinderconcentric with the cavity resonator having a plurality of helicallydisposed slots, means for relatively rotating the cylinders to 6. causeradio waves from an object to scan the opening, thereby correspondinglyto excite the cavity resonator, and means connected with the excitedcavity resonator for producing a likeness of the object.

12. An electric system having, in combination, a'cavity resonator, meansdisposed adjacent to the resonator for causing radio waves from anobject to scan the cavity resonator, thereby to excite the cavityresonator, an oscilloscope having a screen, and means connected with theexcited cavity resonator and controlled in accordance with the scanningfor producing a likeness of the object on the screen.

13. An electric system having, in combination, a radiowave generator forproducing radio waves for transmitting through space, a cavity resonatorprovided with slot means in its outer surface communicating with theinterior of the resonator and resonant to the frequency of thetransmitting means for receiving the transmitted waves, and means forfocusing the received waves on the slot means of the cavity resonator.

14. An electric system having, in combination, a cavity resonatorprovided with an opening, means for focusing radio waves from an object,means for causing the focused waves to scan the opening, therebycorrespondingly to excite the cavity resonator, and means connected withthe excited cavity resonator and controlled in accordance with thefocused radio waves for producing a likeness of the object.

15. An electric system having, in combination, a cavity resonator, amultiplicity of pick-up elements disposed within the cavity resonator,means for causing radio waves from an object to excite the cavityresonator, and means connected with the excited cavity'resonatorcontrolled by the energy in the pick-up elements for producing alikeness of the object.

16. An electric system having, in combination, a cylindrical cavityresonator dimensioned to support a resonant frequency of radio energyand provided with a longitudinally disposed opening of dimensionsresonant to the said frequency, and a cylinder in which the cavityresonator is disposed and provided with successively disposed means forscanning the opening, thereby to excite the cavity resonator.

17. An electric system having, in combination, a cavity resonatordimensioned to support a resonant frequency of radio energy and providedwith an opening, means movable with respect to the cavity resonatorprovided with a plurality of slots of dimensions resonant to the saidfrequency, and means for relatively moving the relatively movable meansand the cavity resonator to cause the plurality of slots to scan theopening, there by correspondingly to excite the cavity resonator.

18. An electric system having, in combination, a cavity resonatordimensioned to support a resonant frequency of radio energy and providedwith an opening, provided with a plurality of slots disposed parallel tothe opening, and means for periodically alining the opening withsuccessive slots.

19. An electric system having, in combination, a cavity resonatordimensioned to support a resonant frequency of radio energy and providedwith an opening of dimensions resonant to the said frequency, and meansfor periodically blocking parts of the opening.

20. An electric system having, in combination, a cavity resonatordimensioned to support a resonant frequency of radio energy and providedwith an opening, means for focusing radio waves corresponding to thesaid frequency on the cavity resonator, and means provided with aplurality of slot antennas for scanning the opening, therebycorrespondingly to excite the cavity resonator.

21. An electric system having, in combination, a cylindrical cavityresonator dimensioned to support a resonant frequency of radio energyand provided with a longitudinally disposed opening, means for focusingradio waves on the cavity resonator, and a cylinder cooperative with thecavity resonator provided with helically disposed means for scanning theopening, thereby correspondingly to excite the cavity resonator.

22. An electric system having, in combination, a cylindrical cavityresonator dimensioned to support a resonant frequency of radio energyand provided with a longitudinally disposed opening, means relativelyrotatable with respect to the cavity resonator provided withsuccessively disposed slot antennas, and means for relatively rotatingthe relatively rotatable means and the cavity resonator to cause thesuccessively disposed slot antennas to scan the opening.

23. An electric system having, in combination, a cavity resonatordimensioned to support a resonant frequency of radio energy and providedwith an openiu coupling means extending into the cavity r onator fortransducing radio energy, and means for rendering various parts of theopening successively effective to permit the passage of radio energytherethrough.

24. An electric system having, in combination, a cylindrical cavityresonator dimensioned to support a resonant frequency of radio energyand having a longitudinally disposed opening, cylindrical means providedwith a plurality of helically disposed slot antennas, means for focusingradio waves upon the cylindrical means, and means for relativelyrotating the cavity resonator and the cylindrical means to cause theheiically disposed slot antennas to scan the opening.

25. An electric system having, in combination, a radiowave generator,means for transmitting the generated waves through space, a cavityresonator resonant to the frequency of the transmitting means andprovided with an opening for receiving the transmitted waves, and meansfor rendering various portions of the opening successively effective toreceive the radio waves.

26. An electric system having, in combination, a cavity resonatorprovided with an opening, means for focusing radio waves from an objectupon the cavity resonator, means for moving the cavity resonator tocause the opening to scan the focused radio waves in one direction,means for scanning the opening in another direction to expose successiveparts of the opening successively to the focused radio energy, means fordetecting the radio energy in the cavity resonator during the scanningprocesses, a cathode-ray tube having a screen successively disposedareas of which correspond respectively to the successive parts of theopening as they are successively exposed, means for producing in thetube an electron stream impinging on the screen, means for causing theelectron stream to scan the successively disposed areas of the screen insynchronism with the scanning processes, and means responsive to thedetecting means and cooperative with the electron-stream-producing meansfor producing a likeness of the object on the screen.

27. An electric system having, in combination, a cavity resonatorprovided with an opening, means for focusing radio Waves from an objecton the cavity resonator, means disposed adjacent to the resonator forcausthe obiect to scan the cavity resonator, thereby to excite thecavity resonator, an oscilloscope having a screen, and means connectedwith the excited cavity resonator and controlled in accordance with thescanning for producing a likeness of the object on the screen.

29. An image reproducing system comprising a polystyrene member forforming a radio image of an object from microwave electromagnetic energyreflected from the object, a cylindrical scanning device having ahelical array of scanning apertures for successively passing microwaveenergy from points of said image to the interior of the cylindricaldevice, means within the cylindrical device responsive to said energyfor developing an electrical signal, means for transmitting said signalsto a receiving station and means including a cathode ray tube at thereceiving station for developing a visible image of the object.

30. An electric system having, in combination, a circular wave guideadapted to support radio waves and provided with slot means, acylindrical sleeve rotatably mounted in closely fitting coaxial relationaround the wave guide and having a plurality of spaced apertures, andmeans for relatively rotating the sleeve and the wave guide whereby theapertures become successively aligned with the slot means to permit thepassage of radio Waves therethrough.

31. An electric system having, in combination, a circular wave-guidecylinder adapted to support radio waves and provided with slot meansextending substantially parallel to the axis of the cylinder, acylindrical sleeve rotatably mounted in closely fitting coaxial relationaround the wave-guide cylinder and having a plurality of spacedapertures, and means for relatively rotating the sleeve and thewave-guide cylinder whereby the apertures become successively alignedwith the slot means to permit the passage of radio waves therethrough.

32. An electric system having, in combination, a circular wave-guidecylinder adapted to support radio waves and provided with slot meansextending substantially parallel to the axis of the cylinder, means forfocusing radio waves upon the wave-guide cylinder, a cylindrical sleeverotatably mounted in closely fitting coaxial relation around thewave-guide cylinder and having a plurality of'spaced apertures, andmeans for relatively rotating the sleeve and the wave-guide cylinderwhereby the apertures become successively aligned with the slot means topermit the passage of the focused radio Waves therethrough.

33. An electric system having, in combination, a hollow substantiallycircular wave-guide cylinder adapted to support radio waves and havingslot means extending substantially parallel to the axis of the cylinderdistances substantially related to the half-Wavelength of the radiowaves, means for focusing radio waves on the wave guide, a cylindricalsleeve rotatably mounted in closely fitting coaxial relation around thewave guide and having a plurality of spaced apertures, and means forrotating the sleeve whereby its apertures are adapted to registersuccessively with the slot means in a predetermined sequence forpermitting radio waves to pass through successive portions of the slotmeans one at a time, the remaining portions of the slot means beingclosed and effectively short-circuited by the sleeve.

34. An electric system having, in combination, a wave guide of the typehaving a transverse cross-sectional configuration to permit the passagetherethrough of radio waves above a critical frequency related to thesaid transverse cross-sectional configuration provided with slot antennameans of dimensions sufiicicnt to pass the said radio waves, and meansfor opening and closing parts of the slot antenna means.

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